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POISON IVY, POISON OAK, AND POISON SUMAC
AND OTHER IRRITATING PLANTS
Poison Ivy is common in Altona Forest especially in open areas and around the trails which are open to the sun.
Following is some information which might be useful to you.
Scientific classification:
Poison ivy, poison oak, and poison sumac belong to the genus Toxicodendron (although they are sometimes considered to be in the genus
Rhus or sumac family) of the family Anacardiaceae. Poison ivy and poison oak are variations of the same plant but some botanists do consider
them as separate species. They differ in the shape of their leaflets. The most common species of poison ivy is Toxicodendron radicans. Poison
Ivy poisoning is called dermatitis or Rhus-dermatitis.
Poison sumac is classified as Toxicodendron vernix. It is a tall, smooth-stemmed shrub that grows in swamps throughout the eastern United
States and southern Canada. The leaves are pinnately compound with seven to thirteen leaflets, including one at the tip. The fruits are white
or yellowish berries in clusters similar to those of poison ivy. Few people come into contact with poison sumac because it is somewhat
isolated in swamps and no poison sumac plants have been found in Altona Forest.
A leaf from a
staghorn sumac is
Poison ivy and sumac are relatives of the tropical Cashew Family, which includes both cashew and pistachio nuts. This family also includes
similar to that of the
the staghorn sumach tree, which is a non irritant and often planted for its bright autumn colour.
poison sumac.
Form:
Poison sumac (T. vernix) is larger than poison ivy. Both poison ivy and sumac may take the form of vines climbing up tree trunks as high as
15 m., or they might remain as shrubs standing erect by themselves, or vines trailing on the forest floor. Poison ivy can often be found to be
more than 1.5 m’s in height if it is left to grow undisturbed.
Poison ivy:
In some areas of north America, the names poison ivy and poison oak are used to describe the same plant.
Poison ivy is a perennial that spreads by seeds and woody rhizomes. Its leaves are alternate and consist of three leaflets;
the middle one has a stalk much longer than those of the two lateral leaflets. The edges of the leaflets may be smooth or
toothed, but they are rarely lobed. The leaves vary greatly in size, from 8 mm to 10 cm long. They are reddish or purplish
when they first emerge in the spring, are green during the summer, and are various shades of yellow, orange, red, or The leaves have
bronze in the autumn. Male and female flowers are normally found on separate plants. They are clustered, small, andthree leaflets.
cream to yellow green in colour. The green to yellow fruits are clustered, round, and waxy. They are 3-7 mm in diameter
Flowers
are small
and
inconspic
ious.
Poison ivy
fruit.
and contain 1-seeded.1
Habitat:
Poison ivy and poison oak are found on roadsides, in thickets, along the edges of woods and meadows, in hedgerows, on sandy, stony, or rocky shores of streams,
rivers, and lakes and open woods. Poison ivy is present in every province except Newfoundland. It is most abundance in southern Ontario and southern Quebec.
Appearance:
Poison Ivy has three leaflets. The leaves are droopy, especially in the spring. It resembles the Virginia Creeper, except that vine has five leaflets.
Distinguishing characteristics include:
•
light grey coloured stems of previous year’s growth,
•
regular arrangement of the three leaflet leaves on the stems,
•
and clusters of small, yellowish or white berrylike fruit that appear in summer and fall and often last over the winter.
Other characteristics, such as the size of the leaflets, leaf margin, shiny or dull surfaces of the leaf, vary considerably.
Poison location and type:
1
Mulligan, G.A.; Junkins, B.E. 1977. The biology of Canadian weeds.
The three plants discussed here, poison ivy, poison oak, and poison sumac contain a lacquerlike resin or oil in their sap which contains four antigenic compounds
(catechols), including one called urushiol, an irritant, which is capable of producing an allergic reaction in about 70% of people. This chemical provokes a
sensitizing reaction in most persons the first time effective contact occurs. It causes a skin eruption that may vary from itching inflammations to watery blisters. 1
The sap is present in roots, stems, leaves, flowers, pollen and fruit. The only parts without the poison are the anthers, xylem, and epidermis. The poisonous sap is
released only after the surface is touched or bruised even slightly. It is easiest to be infected with poison ivy, called Rhus-dermatitis, in the spring and early summer,
when leaves are tender and bruise easily.
The sap is deposited on the skin by direct contact which may be made by brushing past the leaves or the bare stems. The resin or oil can also be carried on anything
that has touched the plant, including shoes, bicycles, clothing, garden tools, sporting equipment, and even the fur of pets. The oil can remain active on these objects
for several months. Smoke from burning poison ivy plants carry the sap and can affect all uncovered parts of the body.
Clothing can be decontaminated by laundering in a washing machine in hot water with soap or detergent. Infected skin can never be washed soon enough to prevent
some Rhus-dermatitis in sensitive individuals, but washing is useful because it minimizes the severity of the rash and also prevents the spread of the sap to
uninfected parts of the body.
Under hot, humid conditions the poisonous sap becomes inert in about a week. However, under dry conditions, the plant can retain its harmful effect for a long
period of time.
When Exposed to Poison Ivy:
Not everyone is equally sensitive to the poison in poison ivy. Some people, about 30%, have no reaction the first time they come in contact with the plant. No person
is completely immune to the poisonous sap and so they often will develop a sensitivity after a number of exposures. Some people are sensitive to small amounts of
the poison, whereas others react only to large amounts. Children usually develop allergic reactions after two or more exposures. It is possible to "grow out” of the
sensitivity with time and with no further contact with the plant. As stated earlier, the toxin in the sap becomes inert in high heat and humidity, so the greatest danger
is during cool, dry weather.
The sap must penetrate the skin before poisoning results; therefore, the most severe poisoning affects areas with thin skin. Symptoms are less severe or do not occur
at all in areas with thick skin or heavy hair.
There is no acceptable method of immunization and no clinical reason, as yet, as to why people react differently to similar amounts of exposure. The interval
between contact and the appearance of the Rhus-dermatitis varies because of the different susceptibilities of individuals and the amount of poisonous liquid
contacting the skin. The first time someone is exposed to poison ivy, it usually takes one to three weeks for the rash, Rhus-dermatitis, to develop. If they are
exposed again, the rash will appear in just 12 to 48 hours. Healing time varies from a few days to several weeks, and healed sites often remain supersensitive to any
further contact with sap for several months.
Symptoms of Poisoning and Treatment:
The first symptom of poisoning is a slight reddening of the skin and a severe itching. Later, a red inflammation and often a blistering of the skin occurs. Often the
blisters are seen in lines indicating the point of contact with the plant. Itching soon becomes intense.
1
http://www.encyclopedia.com/articles/10335.html
In severe cases, oozing sores develop. The rash spreads by the poisonous sap, not as the result of contamination from the watery fluid in the blisters. However,
scratching contaminated areas, slows healing, promotes infection and tends to help spread the toxin. Relief may be found through the application of medication
available in most drugstores. However, severe rashes and blisters, especially those covering large areas or accompanied by headaches and fever, or if sensitive parts
of the body, such as the eyelids are infected, should be examined by a physician immediately. Medical treatment is most effective if applied before the oozing sores
appear.
Poison ivy treatment:
Wash infected skin as soon as possible with cold water to minimize the severity of the rash and prevent the spread of the sap to uninfected parts of the body.
Unfortunately, skin absorbs the active compounds in the sap within the first three minutes, and you cannot prevent the dermatitis without medical treatment.
The rash can be reduced in severity if a strong soap and water, which are superior to water alone in removing the sap, is used to wash the exposed area within five
minutes of contact. All parts of the body should then be washed with soap and water. Sap can get under fingernails, so it is important to wash these areas as well.
Soap also temporarily removes a natural protective layer that helps keep the active compounds from being absorbed through the skin.
Since residual plant oils on clothing can easily recontaminate the victim or others unless it is thoroughly washed, clothing, including shoes, should be removed,
using gloves, as soon as possible and washed in hot, soapy water.
Antihistamine first-aid creams as well as boric acid solution or calamine lotion are commonly used to relieve itching. 2 A tincture (extract in alcohol) of calendula is
also said to relieve the itching. In the woods, it is often possible, in the same habitat as Poison Ivy, to find Jewelweed (Spotted Touch-me-not), whose leaves may be
crushed and immediately rubbed on affected skin to reduce the reaction.
A pharmacist can provide advice on how to relieve some of the symptoms. Applying cool, wet compresses of tap water for 20 to 30 minutes every few hours will
dry the blisters and remove the itch. Oatmeal baths or calamine lotion that has been cooled in the fridge may help to soothe the symptoms.
If a rash does develop, keep the blisters clean and dry. Avoid scratching to prevent infection.
It is a good idea to see a doctor with any case of poison ivy but it is essential if it spreads to the face, eyelids, or to a large part of your body.
Medication to take:
Take medication under the direction of a doctor. However, oral antihistamines such as diphenhydramine (Benadryl) or chlorpheniramine (Chlor-Tripolon) can help
relieve itching but may cause drowsiness.
Check with a pharmacist or doctor before purchasing any products to treat poison ivy.
Destroying poison ivy:
You can destroy poison ivy by cultivation. Pulling poison ivy seldom kills the plant completely, as it consists of a vast interconnected network of above- and
below-ground horizontal rhizomes and above-ground vertical stems. Repeated cultivation will eliminate poison ivy because it does not easily regenerate from plant
2
“Poison Ivy, Poison Oak, and Poison Sumac," Microsoft® Encarta® Online Encyclopedia 2000 http://encarta.msn.com © 1997-2000 Microsoft Corporation.
fragments.
Chemicals are not recommended, but are necessary in areas that do not permit cultivation, where some damage to other vegetation can be tolerated and where the
medical danger is great. Suitable chemicals, ie biodegradable, can be purchased at stores that sell pesticides. Before using chemicals, be aware
of local and provincial ministry of agriculture regulations regarding use.
Be very careful when dealing with these plants. Your boots, protective clothing and implements may pick up the sap and transfer it to your skin.
Do not burn the plants because the soot and smoke will carry the poison. Also, dead poison ivy plants can still cause Rhus- dermatitis and must
be handled with care.
Other irritating plants in Ontario
Forests:
Stinging Nettles (Genus Urtica) also cause skin irritation, though not as seriously as poison ivy. The discomfort may persist for only few
minutes. Nettles have tiny hairs on the stems and leaves, which are razor-sharp and inject the irritant, formic acid, when the ends break off
on contact. These herbs, whose fibres were once woven into cloth, twine and nets (hence the name), are common in waste land, roadsides,
and behind beaches at the edge of forests.
Lady slipper orchids also cause an uncomfortable skin irritation when they are handled, especially if the leaves and stems are wet.
Sources:
Agriculture and Agri-Food Publication 1699/E ©Minister of Supply and Services Canada 1990 Cat.No. A53-1699/1989E ISBN
0-662-17265-5 Printed 1980 Revised 1990
Mulligan, G.A.; Junkins, B.E. The biology of Canadian weeds. 23. Rhus radicans L. Can. J. Plant Sci., 1977
Turner, Nancy J., and Adam F. Szczawinski. Common Poisonous Plants and Mushrooms of North America. Lubrecht & Cramer, 1995.
Venning, Frank D. Wildflowers of North America: A Guide to Field Identification. Golden, 1984.
"Poison Ivy, Poison Oak, and Poison Sumac," Microsoft® Encarta® Online Encyclopedia 2000 http://encarta.msn.com © 1997-2000
Microsoft Corporation.